Linux kernel hardening

From Securityfocus.com: “Is Linux secure? The question is much less useful, than ‘Is Linux “securable?’ The answer to the latter is a definite yes. Being securable means that Linux can be made
more secure (to whatever degree necessary) by applying a clearly defined sequence of steps that always produces the same result, and that can be automated and
applied to systems that have been in operation for a long time.”